2,4-Dichloro-3,5-dimethylfluorobenzene is an intermediate for the preparation of pharmaceutically active compounds of the quinolone carboxylic acid type (see the applicant's earlier German Patent Application No. 197 17 231.8). The preparation of 2,4-dichloro-3,5-dimethylfluorobenzene, however, is not known from the prior art. The applicant's earlier patent application which has been mentioned above describes the preparation of 2,4-dichloro-3,5-dimethylfluorobenzene without the use of co-catalysts.